Question about 1999 Pontiac Grand Prix

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1999 pontiac grand prix gtp w/supercharger

The car will crank up and run great for 20 or 30 sec. then it will start to miss and run like ****. it is like it is staved for gas or getting to much gas. there is alot of black soot on the rim of the tail pipe.and there is a really strong smell of fuel when it gets done spitting and sputtering. i have replaced the fuel filter,pcv valve, new air filter. the 3 front plugs. have not got to the back 3 yet. going to do that now. 12:53 in the a.m. i plugged a actron OBD 2 pocketscan in to the plug and it says no codes found. so where do i go from here. i need all the help i can get. how do i check if it is relay or the egr valve is leaking. how do i test the egr valve. or if it is a defective ECM. what are they, where are they, and how do i test if they are bad? i have a haynes repair manual but it does not have a layout of the 3800 super charged engine to show me where these parts are located. thanks for all and any help.

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  • polisa69 Feb 17, 2009

    I have a very similar problem. I'm troubleshooting it right now, but I also had a similar problem a couple years ago. It ran great and suddenly surged as though I stamped on the accelerator. Then it dropped back to normal for a few seconds and then started to surge repeatedly until it died. There were no codes on the scan and I went so far as to change the fuel pump. (In addition to most of what you listed.) Eventually, after it got to the point where the car would no longer run longer than 20 seconds at a time, a check engine light came on and the scan code was P0300 "Random multiple Misfires" or something like that. It did not point us in the right direction, and no matter how many times we re-set the car, it would only give us this same code. Ultimately, it was traced back to the MAF (Mass Air Flow Sensor) and the problem was solved.


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I had the same problem. My temp light came on on my dash. I hooked up to a computer and it showed that that temp of the car was 248 degrees when the engine is really 165 degrees. It was the computer sensor. The sensor is under the thermostat and was about 15 dollars. It took about 30 mins to change.

Posted on Aug 19, 2008

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No it doesnt sound like a bad ignition.... it would most likely be a bad sensor MAF, MAP, O2,...(mass air flow, manifold apsolute pressure, oxygen sesor) the black smoke is a def. indication of over fueling... other than sesors its possible it could be the fuel pressure regulator......all this depends on the fuel system set up couldnt tell you for sure without looking at the car or the book

Posted on Aug 07, 2008

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Same thing is going on with mine. It sounds like the ignition switch is bad.

Posted on Jul 30, 2008

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